The present invention relates to a golf club, more particularly to a combination of a club head having a specific geometry and a club shaft having a specific variable flexural rigidity, which can increase the traveling distance of the ball.
In case of golfers whose club head speed at impact is high such as pro golfers and advanced golfers, in order to obtain a high trajectory to increase the traveling distance of the ball, a sufficient backspin may be given to the ball even by a golf club having a relatively small loft angle, for example a driver having a loft angle of less than 11 degrees. An ideal driver shot trajectory may be obtained when the backspin is about 2000 rpm and the launch angle is about 12 degrees.
On the other hand, for the golfers whose club head speed at impact is relatively slow such as beginner golfers and intermediate golfers, it is very difficult to get a sufficient backspin with a golf club having a relatively small loft angle such as driver, and therefore, it is difficult to obtain a high trajectory and long traveling distance.
According to a ball hitting test using a swing robot conducted by the inventor, at the club head speed of the average golfers which is about 40 m/s, optimal conditions by which the traveling distance becomes maximum are a launch angle in the range of 14 to 17 degrees, and a backspin in the range of 1700 to 2500 rpm.
In order to increase the launch angle, the drivers for the average golfers are increased in the loft angle in comparison with the drivers for the advanced golfers as an established practice. The average golfers are however, more likely to hit a ball at a position under the sweet spot as the sweet spot shifts toward the top of the clubface with the increase in the loft angle. As a result, the backspin becomes excessively increased by the gear effect, which results in an undesired high trajectory to decrease the carry and run.